Method and apparatus of allocating control information in wireless communication system

ABSTRACT

A method of allocating control information in a wireless communication system is provided. The method includes: allocating essential control information of a first system to a first sub-frame in a frame including a plurality of sub-frames each of which comprises a plurality of orthogonal frequency-division multiplexing (OFDM) symbols; and allocating essential control information of a second system to an n th  sub-frame in a fixed position from the first sub-frame (where n is an integer satisfying n&gt;1). Accordingly, in a frame supporting heterogeneous systems, essential control information can be fixedly allocated to a specific position while maintaining the number of system switching points, at which switching occurs between the systems, to one even if a radio resource allocation amount changes between the systems, and thus the essential control information that must be received by all user equipments can be effectively provided without the increase of overhead.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of US Provisionalapplication No. 61/031,368 filed on Feb. 26, 2008, U.S. Provisionalapplication No. 61/038,040 filed on Mar. 19, 2008, US Provisionalapplication No. 61/038,057 filed on Mar. 20, 2008, and Korean Patentapplication No. 10-2008-0057271 filed on Jun. 18, 2008, all of which areincorporated by reference in their entirety herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless communications, and moreparticularly, to a method of allocating essential control information ina frame supporting heterogeneous systems.

2. Related Art

The institute of electrical and electronics engineers (IEEE) 802.16standard provides a technique and protocol for supporting broadbandwireless access. The standardization had been conducted since 1999 untilthe IEEE 802.16-2001 was approved in 2001. The IEEE 802.16-2001 is basedon a physical layer of a single carrier (SC) called ‘WirelessMAN-SC’.The IEEE 802.16a standard was approved in 2003. In the IEEE 802.16astandard, ‘WirelessMAN-OFDM’ and ‘WirelessMAN-OFDMA’ are further addedto the physical layer in addition to the ‘WirelessMAN-SC’. Aftercompletion of the IEEE 802.16a standard, the revised IEEE 802.16-2004standard was approved in 2004. To correct bugs and errors of the IEEE802.16-2004 standard, the IEEE 802.16-2004/Cor1 (hereinafter, IEEE802.16e) was completed in 2005 in a format of ‘corrigendum’.

Communication between a base station (BS) and a user equipment (UE)includes downlink (DL) transmission from the BS to the UE and uplink(UL) transmission from the UE to the BS. A system profile based on theexisting IEEE 802.16e supports a time division duplex (TDD) scheme inwhich DL transmission and UL transmission are divided in a time domain.In the TDD scheme, UL transmission and DL transmission are performed atdifferent times by using the same frequency band. The TDD scheme has anadvantage in that frequency selective scheduling is simply performedsince a UL channel characteristic and a DL channel characteristic arereciprocal.

At present, there is ongoing standardization effort for the IEEE 802.16mstandard which is a new technical standard based on the IEEE 802.16e.The IEEE 802.16e system considers not only a frequency division duplex(FDD) scheme but also a half-duplex FDD (H-FDD) scheme. In the FDDscheme, DL transmission and UL transmission are simultaneously performedby using different frequency bands. In the H-FDD scheme, DL transmissionand UL transmission are performed at different times by using differentfrequency bands. That is, the H-FDD scheme does not perform DLtransmission and UL transmission simultaneously, and a DL radio resourceand a UL radio resource are not allocated to a UE using the H-FDD schemein the same time domain.

An evolution system evolved from a legacy system has to be designed tooperate by incorporating the legacy system, which is referred to asbackward compatibility. To satisfy the backward compatibility, theevolution system has to be able to support not only the TDD scheme butalso the FDD scheme, the H-FDD scheme, etc. As various transmissionschemes are supported, essential control information needs to beprovided for each of the legacy system and the evolution system. Theessential control information is control information that must beacquired by all UEs using the system. Examples of the essential controlinformation include system information to be broadcast, synchronizationinformation, etc. The essential control information for the evolutionsystem is preferably provided without having an effect on the essentialcontrol information of the legacy system.

However, how to allocate the essential control information in theevolution system satisfying backward compatibility with the legacysystem is not provided yet.

SUMMARY OF THE INVENTION

The present invention provides a method of allocating essential controlinformation in a frame supporting heterogeneous systems.

According to an aspect of the present invention, a method of allocatingcontrol information in a wireless communication system is provided. Themethod includes: allocating essential control information of a firstsystem to a first sub-frame in a frame including a plurality ofsub-frames each of which comprises a plurality of orthogonalfrequency-division multiplexing (OFDM) symbols; and allocating essentialcontrol information of a second system to an n^(th) sub-frame in a fixedposition from the first sub-frame (where n is an integer satisfyingn>1).

According to an aspect of the present invention, a method of allocatingcontrol information in a wireless communication system is provided. Themethod includes: allocating at least one sub-frame for a first system ina downlink frame including a plurality of sub-frames; allocating atleast one sub-frame contiguous in a time domain for a second system tothe sub-frame for the first system; allocating essential controlinformation of the first system to the sub-frame for the first system;and allocating essential control information of the second system to thesub-frame for the second system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows an example of a frame structure.

FIG. 3 shows an example of a frame including a plurality ofpermutations.

FIG. 4 shows an example of a frame supporting heterogeneous systems.

FIG. 5 shows another example of a frame supporting heterogeneoussystems.

FIG. 6 shows another example of a frame supporting heterogeneoussystems.

FIG. 7 shows another example of a frame supporting heterogeneoussystems.

FIG. 8 shows another example of a frame supporting heterogeneoussystems.

FIG. 9 shows another example of a frame supporting heterogeneoussystems.

FIG. 10 shows another example of a frame supporting heterogeneoussystems.

FIG. 11 shows an example of control information in a frame supportingheterogeneous systems.

FIG. 12 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 13 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 14 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 15 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 16 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 17 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 18 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 19 shows an example of control information in a frequency divisionduplex (FDD) frame.

FIG. 20 shows an example of control information in a half-duplex FDD(H-FDD) frame.

FIG. 21 shows an example of control information on a complementarygrouping and scheduling (CGS)-based H-FDD frame.

FIG. 22 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 23 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 24 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 25 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 26 shows another example of control information in a framesupporting heterogeneous systems.

FIG. 27 shows an example of a super-frame supporting heterogeneoussystems.

FIG. 28 shows another example of a super-frame supporting heterogeneoussystems.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system. The wireless communicationsystem can be widely deployed to provide a variety of communicationservices, such as voices, packet data, etc.

Referring to FIG. 1, the wireless communication system includes at leastone user equipment (UE) 10 and a base station (BS) 20. The UE 10 may befixed or mobile, and may be referred to as another terminology, such asa mobile station (MS), a user terminal (UT), a subscriber station (SS),a wireless device, etc. The BS 20 is generally a fixed station thatcommunicates with the UE 10 and may be referred to as anotherterminology, such as a node-B, a base transceiver system (BTS), anaccess point, etc. There may be one or more cells within the coverage ofthe BS 20.

A downlink (DL) represents a communication link from the BS 20 to the UE10, and an uplink (UL) represents a communication link from the UE 10 tothe BS 20. In the DL, a transmitter may be a part of the BS 20, and areceiver may be a part of the UE 10. In the UL, the transmitter may be apart of the UE 10, and the receiver may be a part of the BS 20.

There is no restriction on the multiple access scheme used in thewireless communication system. Examples of the multiple access schemeare various, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiplex access (FDMA),single-carrier FDMA (SC-FDMA), and orthogonal frequency divisionmultiple access (OFDMA).

The BS 20 has at least one cell. The cell is an area in which the BS 20provides a communication service. Different communication schemes can beused in one cell. That is, heterogeneous wireless communication systemsmay exist while sharing a communication service area. Hereinafter, theheterogeneous wireless communication systems or heterogeneous systemsrefer to systems using different communication schemes. For example, theheterogeneous systems may be systems using different access schemes, ormay be a legacy system and an evolution system supporting backwardcompatibility with the legacy system.

FIG. 2 shows an example of a frame structure. A frame is a data sequenceused according to a physical specification in a fixed time duration.This is a logical frame, and the section 8.4.4.2 of the IEEE standard802.16-2004 “Part 16: Air Interface for Fixed Broadband Wireless AccessSystems” may be incorporated herein by reference.

Referring to FIG. 2, a frame includes a downlink (DL) frame and anuplink (UL) frame. DL transmission is performed through the DL frame,and UL transmission is performed through UL frame. In a time divisionduplex (TDD) scheme, UL and DL transmissions are achieved at differenttimes but share the same frequency band. The DL frame temporallyprecedes the UL frame. The DL frame includes a preamble, a frame controlheader (FCH), a DL-MAP, a UL-MAP, and a burst region, in that order.Guard times are provided to identify the UL frame and the DL frame andare inserted to a middle portion (between the DL frame and the UL frame)and a last portion (next to the UL frame) of the frame. Atransmit/receive transition gap (TTG) is a gap between a DL burst and asubsequent UL burst. A receive/transmit transition gap (RTG) is a gapbetween a UL burst and a subsequent DL burst.

The preamble is used between a BS and a UE for initial synchronization,cell search, and frequency-offset and channel estimation. The FCHincludes information on a length of a DL-MAP message and a coding schemeof the DL-MAP.

The DL-MAP is a region for transmitting the DL-MAP message. The DL-MAPmessage defines access to a DL channel. The DL-MAP message includes aconfiguration change count of a downlink channel descriptor (DCD) and aBS identifier (ID). The DCD describes a DL burst profile applied to acurrent MAP. The DL burst profile indicates characteristics of a DLphysical channel. The DCD is periodically transmitted by the BS by usinga DCD message.

The UL-MAP is a region for transmitting a UL-MAP message. The UL-MAPmessage defines access to a UL channel. The UL-MAP message includes aconfiguration change count of an uplink channel descriptor (UCD) andalso includes an effective start time of uplink allocation defined bythe UL-MAP. The UCD describes an uplink burst profile. The uplink burstprofile indicates characteristics of a UL physical channel and isperiodically transmitted by the BS by using a UCD message.

Hereinafter, a slot is a minimum possible data allocation unit, and isdefined with a time and a subchannel. The number of subchannels dependson an FFT size and time-frequency mapping. The subchannel includes aplurality of subcarriers, and the number of subcarriers per subchanneldiffers depending on a permutation rule. Permutation is mapping of alogical subchannel onto a physical subchannel. In full usage ofsubchannels (FUSC), the subchannel includes 48 subcarriers. In partialusage of subchannels (PUSC), the subchannel includes 24 or 16subcarriers. A segment is at least one subchannel group.

Mapping of data onto a physical subcarrier in a physical layer isperformed in two steps in general. In the first step, data is mapped toat least one data slot on at least one logical subchannel. In the secondstep, each logical subchannel is mapped to the physical subcarrier. Thisis called permutation. A permutation rule such as FUSC, PUSC,optional-FUSC (O-FUSC), optional-PUSC (O-PUSC), adaptive modulation andcoding (AMC), etc., is disclosed in Document 1. A group of orthogonalfrequency-division multiplexing (OFDM) symbols using the samepermutation rule is referred to as a permutation zone. One frameincludes at least one permutation zone.

The FUSC and the O-FUSC are used only in DL transmission. The FUSCconsists of one segment including all subchannel groups. Each subchannelis mapped to a physical subcarrier distributed across the entirephysical channel. This mapping changes in each OFDM symbol. A slotconsists of one subchannel on one OFDM symbol. Pilots are allocated byusing different schemes in the O-FUSC and the FUSC.

The PUSC is used both in DL transmission and UL transmission. In DL,each physical channel is divided by a cluster consisting of 14contiguous subcarriers on 2 OFDM symbols. 6 groups of physical channelsare mapped. In each group, a pilot is allocated in a fixed position toeach cluster. In UL, subcarriers are divided by a tile consisting of 4contiguous physical subcarriers on 3 OFDM symbols. A subchannel includes6 tiles. The pilot is allocated to a corner of each tile. The O-PUSC isused only for UL transmission, and the tile consists of 3 contiguousphysical subcarriers on 3 OFDM symbols. The pilot is allocated to acenter of the tile. The pilot can also be referred to as a referencesignal.

FIG. 3 shows an example of a frame including a plurality ofpermutations. The frame is a physical frame. The section 8.4.4.2 of IEEEstandard 802.16-2004 may be incorporated herein by reference.

Referring to FIG. 3, a preamble, an FCH, and a DL-MAP of a DL frame mustappear in every frame. The FCH and the DL-MAP use a PUSC permutation. Inthe DL frame, PUSC, FUSC, selective PUSC, and AMC permutations canappear. The permutation that appears in the DL frame can be defined inthe DL-MAP. The PUSC, selective PUSC, AMC permutations can appear in aUL frame. The permutation that appears in the UL frame can be defined ina UL-MAP.

In a logical frame structure, the permutation rule can be selected byconsidering a frequency diversity gain, a scheduling gain, pilotoverhead, multiple-antenna applicability, adaptive antennaapplicability, etc. A region in which the same permutation rule is usedis referred to as a permutation zone. A plurality of permutation zonesare divided in a time domain. Switching of the permutation zone isdefined in the DL-MAP or the UL-MAP. A type of the permutation used inthe UL frame and the DL frame is not limited, and thus can changevariously.

Table 1 shows exemplary parameters for a frame.

TABLE 1 Transmission Bandwidth 5 10 20 (MHz) Over-sampling factor 28/25Sampling Frequency(MHz) 5.6 11.2 22.4 FFT Size 512 1024 2048 Sub-carrierSpacing(kHz) 10.94 OFDM symbol time, Tu(us) 91.4 OFDM Idle Cyclic Tssymbols time Prefix (CP) (us) per Frame (us) Tg = ¼ Tu 91.4 + 22.85 =114.25 43 87.25 Tg = ⅛ Tu 91.4 + 11.42 = 102.92 48 64.64 Tg = 1/16 Tu91.4 + 5.71 = 97.11 51 47.39 Tg = 1/32 Tu 91.4 + 2.86 = 94.26 53 4.22

The preamble, FCH, DL-MAP, or the like of each frame can be used tocorrectly acquire data or control information in the frame. Thepreamble, the FCH, and the DL-MAP can be regarded as essential controlinformation required by a UE to perform communication by accessing anetwork of a system. The frame may have a size of 5 ms. The essentialcontrol information is allocated temporally first in the frame.

Hereinafter, a frame supporting heterogeneous systems will be described.

The proposed frame is for a case where the heterogeneous systems share afrequency band, and is not limited to a type or definition of theheterogeneous systems. The heterogeneous systems may be two or morewireless communication systems. For convenience of explanation, it isassumed that two wireless communication systems are multiplexed as theheterogeneous system, and any one of the two systems is defined as asystem A and the other system is defined as a system B. The system A maybe a legacy system, and the system B may be an evolution systemsupporting backward compatibility with the system A. For example, thesystem A may imply a wireless communication system using the IEEE802.16e standard technique, and the system B may imply a wirelesscommunication system using the IEEE 802.16m standard technique. It isassumed that the system A and the system B share a frequency band bybeing multiplexed using a time division multiplexing (TDM) scheme. TheTDM scheme uses a radio resource by diving it in a time domain at thesame frequency band.

In addition, it is assumed that the radio resource is allocated in asub-frame unit including a plurality of OFDM symbols in the framesupporting the heterogeneous systems. The sub-frame is a minimum unit ofconstituting the frame and can be defined as a plurality of OFDMsymbols. The sub-frame can be a unit of dividing a DL frame and a ULframe by using a TDD scheme in which the DL frame and the UL frame aretemporally divided. The sub-frame may be a unit of dividing a resourceregion for the system A and a resource region for the system B in theframe. When radio resource allocation and scheduling are performed inthe sub-frame unit, there is an advantage in that transmission delay canbe reduced in data retransmission of a hybrid automatic repeat request(HARQ).

In the system A and the system B, UL transmission and DL transmissioncan be performed by using a time division duplex (TDD) scheme, afrequency division duplex (FDD) scheme, and a half-duplex FDD (H-FDD)scheme. In the TDD scheme, the UL and DL transmissions are performed atdifferent times by using the same frequency band. In the FDD scheme, ULand DL transmissions are performed simultaneously by using differentfrequency bands. In the H-FDD scheme, UL and DL transmissions areperformed at different times by using different frequency bands.

FIG. 4 shows an example of a frame supporting heterogeneous systems. Inthis case, a system A and a system B use a TDD scheme.

Referring to FIG. 4, the frame includes a DL frame and a UL frame. Inthe TDD scheme, the DL frame temporally precedes the UL frame. The DLframe and the UL frame include a plurality of sub-frames. The sub-frameincludes the plurality of OFDM symbols. The plurality of sub-frames areused as sub-frames for the system A and sub-frames for the system B.That is, the DL frame and the UL frame include the sub-frames for thesystem A and the sub-frames for the system B in a specific ratio. It isassumed that all sub-frames for the system A in the DL frame or the ULframe are referred to as a resource region for the system A, and allsub-frames for the system B are referred to as a resource region for thesystem B. The sub-frame is a minimum unit of determining a ratio of aradio resource allocated for the system A to a radio resource allocatedfor the system B in the DL frame or the UL frame.

For explanation, it is assumed that the DL frame include 5 sub-frames,and the UL frame include 3 sub-frames. In the DL frame, A:B which is aratio of the sub-frames for the system A to the sub-frames for thesystem B can be defined variously such as 4:1, 3:2, 2:3, 1:4. A boundarybetween the sub-frame for the system A and the sub-frame for the systemB is referred to as a system switching point (SSP). A resourceallocation method depending on a system may change when the SSP is usedas the boundary in the frame. For example, when using the SSP as theboundary, a permutation rule such as PUSC, FUSC, AMC, etc., may be usedin the resource region for the system A, and a newly defined permutationrule may be used in the resource region for the system B. A position ofthe SSP in the frame may change depending on a change of a ratio of thesub-frame for the system A to the sub-frame for the system B.

FIG. 5 shows another example of a frame supporting heterogeneoussystems. In this case, a system A and a system B use an FDD scheme.

Referring to FIG. 5, the frame is an FDD-type frame in which a DL frameand a UL frame are divided in a frequency domain. The DL frame and theUL frame are multiplexed using a TDM scheme in which a sub-frame for thesystem A and a sub-frame for the system B are divided temporally. Wheneach of the DL frame and the UL frame includes 5 sub-frames, A:B whichis a ratio of the sub-frame for the system A to the sub-frame for thesystem B can be defined variously such as 4:1, 3:2, 2:3, 1:4.

Meanwhile, when the sub-frame for the system A and the sub-frame for thesystem B are multiplexed using the TDM scheme in the DL frame, thesub-frames may be multiplexed using the FDM scheme in the UL frame.

FIG. 6 shows another example of a frame supporting heterogeneoussystems. In this case, regarding an FDD-type frame, a sub-frame for asystem A and a sub-frame for a system B are multiplexed using an FDMscheme in a UL frame.

Referring to FIG. 6, the frame is an FDD-type frame in which a DL frameand a UL frame are divided in a frequency domain. In the DL frame, theDL sub-frame for the system A and the DL sub-frame for the system B aremultiplexed using a TDM scheme in which the sub-frames are dividedtemporally. On the other hand, in the UL frame, the UL sub-frame for thesystem A and the UL sub-frame for the system B are multiplexed using theFDM scheme in which the sub-frames are divided spectrally.

When the DL frame includes 5 sub-frames, A:B which is a ratio of the DLsub-frame for the system A to the DL sub-frame for the system B in theDL frame can be defined variously such as 4:1, 3:2, 2:3, 1:4. In the DLframe, a position of SSP changes according to the ratio of the DLsub-frame for the system A to the DL sub-frame for the system B. Sincethe UL sub-frame for the system A and the UL sub-frame for the system Bare multiplexed using the FDM scheme in the UL frame, the number of ULsub-frames for the system A is equal to the number of UL sub-frames forthe system B.

FIG. 7 shows another example of a frame supporting heterogeneoussystems. In this case, there is no restriction on a UL frame in anFDD-type frame.

Referring to FIG. 7, in the FDD-type frame of FIG. 5, the number ofsub-frames for a system A and the number of sub-frames for a system Bare defined to be equal to each other in a DL frame and a UL frame. Thatis, an SSP is equally applied in the DL frame and the UL frame. However,in the FDD-type frame of FIG. 6, the UL sub-frame for the system A andthe UL sub-frame for the system B are multiplexed using an FDM scheme,and the SSP is applied only in the DL frame.

As such, in the FDD-type frame, the number of sub-frames for the systemA and the number of sub-frames for the system B may be determined to bedifferent from each other in the DL frame and the UL frame, and thus theposition of SSP may be determined differently. In the UL frame, a methodof multiplexing the sub-frame for the system A and the sub-frame for thesystem B may not be limited, and when considering only the DL frame, theFDD frame can be represented as illustrated. In this case, the positionof SSP changes according to a ratio of the DL sub-frame for the system Ato the DL sub-frame for the system B in the DL frame.

FIG. 8 shows another example of a frame supporting heterogeneoussystems. In this case, a system A and a system B use an H-FDD scheme.

Referring to FIG. 8, since the H-FDD scheme performs DL transmission andUL transmission at different times by using different frequency bands, aDL frame and a UL frame occupy different frequency regions and differenttime regions. In the DL frame, the DL sub-frame for the system A and theDL sub-frame for the system B can be multiplexed with various ratios byusing a TDM scheme, and a position of SSP is determined according to theratios. In the UL frame, a sub-frame multiplexing scheme is notparticularly limited.

FIG. 9 shows another example of a frame supporting heterogeneoussystems. In this case, a system A uses a TDD scheme, and a system B usesan FDD scheme.

Referring to FIG. 9, since the system A uses the TDD scheme, DL and ULframes of the system A are divided in a time domain. Since the system Buses the FDD scheme, DL and UL frames of the system B are divided in afrequency domain. The DL sub-frame for the system A and the DL/ULsub-frame for the system B can be multiplexed using a TDM scheme in theDL frame. A ratio of the DL sub-frame for the system A and the DLsub-frame for the system B can be defined variously. Since the system Buses the FDD scheme, the number of DL sub-frames for the system B isequal to the number of UL sub-frames for the system B. In the UL frame,a sub-frame multiplexing scheme is not particularly limited.

In the above description, a transmission scheme in which DL transmissionand UL transmission are divided in a time domain or a frequency domainmay be used identically or differently in the system A and the system B.In addition to the aforementioned transmission scheme, (A, B) which is acombination of a transmission scheme of the system A and a transmissionscheme of the system B can be applied variously such as (FDD, TDD),(H-FDD, FDD), (H-FDD, TDD), (FDD, H-FDD), (TDD, H-FDD), etc., and thesystem A and the system B can be multiplexed according to theaforementioned scheme.

FIG. 10 shows another example of a frame supporting heterogeneoussystems. In this case, the number of system switching points (SSPs)changes when a ratio of a sub-frame for the system A to a sub-frame forthe system B is constant.

Referring to FIG. 10, it is assumed that A:B which is a ratio of a DLsub-frame for the system A to a DL sub-frame for the system B is 3:2 ina DL frame including 5 sub-frames. The number of SSPs may differdepending on arrangement of the DL sub-frame for the system A and the DLsub-frame for the system B. When sub-frames for the same system arearranged consecutively, one SSP is provided for the system A and thesystem B in the DL frame. However, when the sub-frames for the samesystem are distributed and thus the sub-frames for the system A and thesystem B are multiplexed in the arrangement, two or more SSPs arepresent in the DL frame.

When switching between systems occurs frequently in one frame, aparameter for the systems has to change frequently. This may result inthe increase of complexity of an algorithm and the increase of systemoverhead, thereby deteriorating transmission efficiency. Therefore,there is a need to minimize the number of SSPs in one frame. That is, itis preferable to have one SSP by arranging the sub-frame for the systemA and the sub-frame for the system B consecutively in a frame supportingthe system A and the system B.

Now, a method of allocating essential control information in a framesupporting two or more systems will be described. In a frame supportinga system A and a system B, it is assumed that essential controlinformation of the system A is allocated to a DL sub-frame for thesystem A, and essential control information of the system B is allocatedto a DL sub-frame for the system B. The essential control information iscontrol information that must be acquired by a UE using a correspondingsystem. For example, the essential control information may be controlinformation that must be acquired to perform initial cell searchperformed initially after the UE is powered on or non-initial cellsearch for performing handover or neighbor cell measurement. Examples ofthe essential control information include a preamble, an FCH, aDL-MAP/UL-MAP, etc. In addition thereto, the essential controlinformation may be system information, synchronization information, orthe like which is broadcast. Since the essential control information istransmitted through a DL frame from a BS to a UE, a multiplexing schemeof the heterogeneous systems is not limited in the UL frame. In the ULframe, the heterogeneous systems can be multiplexed using variousschemes, such as a TDM scheme, an FDM scheme, a CDM scheme, etc.

FIG. 11 shows an example of control information in a frame supportingheterogeneous systems. In this case, essential control information of asystem A and essential control information of a system B are allocatedin a fixed position in a frame in which the system A and the system Buse a TDD scheme.

Referring to FIG. 11, when a DL frame includes 5 sub-frames, it isassumed that the essential control information of the system A isallocated to a first DL sub-frame, and the essential control informationof the system B is fixedly allocated to a third DL sub-frame. Since eachessential control information has to be allocated in a DL sub-frame of acorresponding system, the first DL sub-frame to which the essentialcontrol information of the system A is allocated is always a DLsub-frame for the system A, and the third DL sub-frame to which theessential control information of the system B is allocated is always aDL sub-frame for the system B. If A:B which is a ratio of the DLsub-frame for the system A to the DL sub-frame for the system B is 4:1or 3:2, two SSPs are present, and if A:B is 2:3 or 1:4, one SSP ispresent.

When the essential control information of the system A and the essentialcontrol information of the system B are allocated in a fixed position inthe frame, a position of the essential control information does notchange even if there is a change in the ratio of the DL sub-frame forthe system A to the DL sub-frame for the system B. Therefore, a UE doesnot have to be informed of a specific offset value to indicate theposition of the essential control information. In addition, it ispossible to solve a problem in that the UE has to re-perform an initialnetwork entry process in order to acquire the essential controlinformation.

For example, in a DL frame having one SSP, it is assumed that theessential control information of the system A is allocated fixedly tothe first sub-frame, whereas the essential control information of thesystem B is allocated to a sub-frame adjacent to the SSP. As the ratioof the DL sub-frame for the system A to the DL sub-frame for the systemB changes, the position of the essential control information of thesystem B changes. In this case, the position of the essential controlinformation of the system B has to be informed by using the specificoffset value according to the essential control information of thesystem A. If the position of the essential control information of thesystem B is not indicated by the offset value, the UE has to re-performthe initial network entity process in order to acquire the essentialcontrol information of the system B. This may be a cause of delaying aprocess which is performed by the UE to acquire the essential controlinformation of the system B. Such a problem does not occur when theessential control information of the system A and the system B isallocated in a fixed position in the DL frame.

FIG. 12 shows another example of control information in a framesupporting heterogeneous systems. In this case, essential controlinformation of a system A and essential control information of a systemB are allocated in a fixed position in a frame in which the system A andthe system B use an FDD scheme.

Referring to FIG. 12, when a DL frame includes 5 sub-frames in an FDDframe, it is assumed that the essential control information of thesystem A is allocated to a first DL sub-frame, and the essential controlinformation of the system B is fixedly allocated to a third DLsub-frame. If A:B which is a ratio of the DL sub-frame for the system Ato the DL sub-frame for the system B is 4:1 or 3:2, two SSPs arepresent, and if A:B is 2:3 or 1:4, one SSP is present. Since a positionof the essential control information does not change even if the ratioof the DL sub-frame for the system A to the DL sub-frame for the systemB changes, a UE does not have to be informed of a specific offset valueto indicate the position of the essential control information, and theUE does not have to re-perform an initial network entry process toacquire the essential control information.

However, when the essential control information of the system B isallocated fixedly to the third DL sub-frame among the 5 DL sub-frames,there is a case where two SSPs are present according to the ratio of theDL sub-frame for the system A to the DL sub-frame for the system B. Whenit is determined to use a plurality of SSPs in one frame, frequentshifting between the systems results in the increase of complexity of analgorithm and the decrease of system efficiency. Therefore, it ispreferable to minimize the number of SSPs while allocating the essentialcontrol information in the frame.

FIG. 13 shows another example of control information in a framesupporting heterogeneous systems. In this case, essential controlinformation of a system B is allocated fixedly to a temporally lastsub-frame of a DL frame in a frame in which a system A and the system Buse a TDD scheme.

Referring to FIG. 13, when the DL frame includes 5 sub-frames, essentialcontrol information of the system A is allocated to a first DLsub-frame, and the essential control information of the system B isallocated to a fifth DL sub-frame, i.e., fixedly allocated to atemporally last DL sub-frame. The essential control information of thesystem A and the essential control information of the system B arerespectively allocated to DL sub-frames located at both ends of the DLframe. In a TDD-type frame, the essential control information of thesystem B is allocated to a DL sub-frame adjacent to a transmit/receivetransition gap (TTG) which is a guard time between the DL frame and theUL frame.

As such, when the essential control information of the system A and theessential control information of the system B are allocated to the DLsub-frames located at both ends of the fixed DL frame, the number ofSSPs can be maintained to one always even if a ratio of the DL sub-framefor the system A and the DL sub-frame for the system B changes.Therefore, a UE does not have to be informed of a specific offset valueto indicate a position of the essential control information, and theincrease of complexity of an algorithm due to frequent shifting of thesystems can be avoided.

FIG. 14 shows another example of control information in a framesupporting heterogeneous systems. In this case, in a frame in which asystem A and a system B use an FDD scheme, essential control informationof the system B is allocated fixedly to a temporally last sub-frame in aDL frame.

Referring to FIG. 14, when essential control information of the system Aand the essential control information of the system B are respectivelyallocated to DL sub-frames located at both ends of the DL frame, thenumber of SSPs can be maintained to one always in a frame in which thesystem A and the system B use an FDD scheme even if a ratio of the DLsub-frame for the system A to the DL sub-frame for the system B changes.Therefore, a UE does not have to be informed of a specific offset valueto indicate a position of the essential control information, and theincrease of complexity of an algorithm due to frequent shifting of thesystems can be avoided.

FIG. 15 shows another example of control information in a framesupporting heterogeneous systems. In this case, essential controlinformation is allocated in a fixed position in a TDD frame byconsidering a variation range of a ratio of a DL sub-frame for a systemA to a DL sub-frame for a system B.

Referring to FIG. 15, when a DL frame of a frame in which the system Aand the system B use a TDD scheme includes 5 sub-frames, it is assumedthat A:B which is a ratio of a DL sub-frame for the system A to a DLsub-frame for the system B changes with a variation range of 3:2, 2:3,and 1:4. The number of DL sub-frames for the system is in the range of 1to 3, and the number of DL sub-frames for the system B is in the rangeof 2 to 4.

The essential control information of the system B is allocated fixedlyto a position separated from a last DL sub-frame of the DL frame by aminimum number of DL sub-frames for the system B. Since at least two DLsub-frames are allocated for the system B, the essential controlinformation of the system B is allocated fixedly to a second last DLsub-frame from a last DL sub-frame of the DL frame. The essentialcontrol information of the system A may always be allocated fixedly to afirst DL sub-frame, or may be allocated fixedly to a DL sub-frameseparated from a first DL sub-frame by a minimum number of DL sub-framesfor the system A.

As such, the number of SSPs can always be maintained to one by fixedlyallocating the essential control information of the system B to a DLsub-frame separated from a last DL sub-frame by a minimum number of DLsub-frames for the system B. Therefore, an advantage of allocating theessential control information in a fixed position and an advantage ofminimizing the number of SSPs can be both achieved.

FIG. 16 shows another example of control information in a framesupporting heterogeneous systems. In this case, essential controlinformation is allocated in a fixed position in an FDD frame byconsidering a variation range of a ratio of a DL sub-frame for a systemA to a DL sub-frame for a system B.

Referring to FIG. 16, in a frame in which the system A and the system Buse the FDD scheme, the number of SSPs can always be maintained to oneby fixedly allocating the essential control information of the system Bto a DL sub-frame separated from a last DL sub-frame by a minimum numberof DL sub-frames for the system B. The essential control information ofthe system A may always be allocated fixedly to a first DL sub-frame, ormay be allocated fixedly to a DL sub-frame separated from a first DLsub-frame by a minimum number of DL sub-frames for the system A.Therefore, an advantage of allocating the essential control informationin a fixed position and an advantage of minimizing the number of SSPscan be both achieved.

FIG. 17 shows another example of control information in a framesupporting heterogeneous systems. In this case, essential controlinformation is allocated in a fixed position in a TDD frame withoutconsidering a variation range of a ratio of a DL sub-frame for a systemA to a DL sub-frame for a system B.

Referring to FIG. 17, in a case where the variation range of the ratioof the DL sub-frame for the system A and the DL sub-frame for the systemB is not considered in the TDD frame, essential control information ofthe system A is allocated fixedly to a first DL sub-frame as shown inFIG. 13, and essential control information of the system B is allocatedfixedly to a last DL sub-frame, and thus the number of SSPs can bemaintained to one.

FIG. 18 shows another example of control information in a framesupporting heterogeneous systems. In this case, essential controlinformation is allocated in a fixed position in an FDD frame withoutconsidering a variation range of a ratio of a DL sub-frame for a systemA to a DL sub-frame for a system B.

Referring to FIG. 18, in a case where the variation range of the ratioof the DL sub-frame for the system A and the DL sub-frame for the systemB is not considered in the FDD frame, essential control information ofthe system A is allocated fixedly to a first DL sub-frame as shown inFIG. 13, and essential control information of the system B is allocatedfixedly to a last DL sub-frame, and thus the number of SSPs can bemaintained to one.

Hereinafter, allocation of essential control information in a frameusing a complementary grouping and scheduling (CGS)-based H-FDD schemewill be described. The CGS-based H-FDD scheme is for the effective useof a radio resource wasted in the H-FDD scheme in which DL transmissionand UL transmission have to be performed at different times by usingdifferent frequency bands. First, the CGS-based H-FDD scheme will bedescribed in comparison with an FDD scheme and the H-FDD scheme.

FIG. 19 shows an example of control information in an FDD frame. FIG. 20shows an example of control information in an H-FDD frame. FIG. 21 showsan example of control information on a CGS-based H-FDD frame.

Referring to FIG. 19 to FIG. 21, in the FDD-type frame in the viewpointof a BS, a DL frame and a UL frame are divided in a frequency domain. DLtransmission and UL transmission are performed simultaneously by usingdifferent frequency bands. Essential control information can betransmitted through sub-frames with a specific spacing in a DL frame.

In the H-FDD-type frame in the viewpoint of the BS, a DL frame and a ULframe are divided in a frequency domain and a time domain. DLtransmission and UL transmission are performed at different times byusing different frequency bands. Essential control information can betransmitted through sub-frames with a specific spacing in a DL frame. Inthe H-FDD scheme, since UL transmission cannot be performed while DLtransmission is performed, an unused resource region is present, andthus a radio resource is wasted to that extent.

In the CGS-based H-FDD scheme, when UEs are divided into a plurality ofgroups so that a DL sub-frame is allocated to UEs of a first group, a ULsub-frame is allocated to UEs of a second group, and when a UL sub-frameis allocated to the UEs of the first group, a DL sub-frame is allocatedto the UEs of the second group. That is, a DL radio resource and a ULradio resource are alternately allocated to the UEs of the first groupand the UEs of the second group. In the viewpoint of the UEs of thefirst group, the H-FDD scheme in which DL transmission and ULtransmission are performed at different frequency bands at differenttimes is satisfied. In addition, the H-FDD scheme is also satisfied inthe viewpoint of the second group. In the CGS-based H-FDD scheme, sinceDL transmission and UL transmission are performed simultaneously in theviewpoint of the BS, a waste of radio resources can be reduced. However,since essential control information has to be received simultaneously bythe UEs of the first group and the UEs of the second group, a sub-frameto which the essential control information is allocated is used as thesame DL sub-frame by the UEs of the two groups.

Now, allocation of essential control information when a CGS-based H-FDDscheme is applied in a frame supporting heterogeneous systems will bedescribed.

FIG. 22 shows another example of control information in a framesupporting heterogeneous systems.

Referring to FIG. 22, it is assumed that a system A uses an FDD scheme,and a system B uses a CGS-based H-FDD scheme. Essential controlinformation of the system A is allocated fixedly to a first DL sub-framein a DL frame, and essential control information of the system B isallocated fixedly to a last DL sub-frame in the DL frame. Since thesystem B uses the CGS-based H-FDD scheme, for the remaining sub-framesother than a sub-frame of a time domain to which the essential controlinformation is allocated, a DL sub-frame for a first group of the systemB and a UL sub-frame for a second group of the system B are allocated inthe same time domain, and a UL sub-frame for the first group of thesystem B and a DL sub-frame for the second group of the system B areallocated in the same time domain.

As such, by allocating the essential control information of the system Busing the CGS-based H-FDD scheme to a last DL sub-frame of the DL frame,the number of SSPs can always be maintained to one even if there is achange in a ratio of a DL sub-frame for the system A to a DL sub-framefor the system B.

In addition thereto, (A, B) which is a combination of a transmissionscheme of the system A and a transmission scheme of the system B can beapplied variously such as (TDD, CGS-based H-FDD), (CGS-based H-FDD,CGS-based H-FDD), etc. Even in this case, by allocating the essentialcontrol information to a last DL sub-frame of a DL frame, the number ofSSPs can always be maintained to one irrespective of the ratio of the DLsub-frame for the system A to the DL sub-frame for the system B.

In the aforementioned frame supporting the heterogeneous systems, thesystem B is multiplexed with respect to the system A. That is, in theaforementioned frame structure, the heterogeneous systems are supportedin the viewpoint of the system A. For example, if the system A is alegacy system and the system B is an evolution system, it is assumedthat the system A is allocated temporally prior to the system B forbackward compatibility in the frame and then the system B isadditionally allocated. However, the frame implies a data sequenceduring a specific time period in a continuous data transmission process,and thus a system that is temporally prior to the other system in theframe may differ depending on a definition on the frame.

Hereinafter, a frame structure supporting heterogeneous systems definedin the viewpoint of each system will be described.

FIG. 23 shows another example of control information in a framesupporting heterogeneous systems. FIG. 24 shows another example ofcontrol information in a frame supporting heterogeneous systems. Theframe of FIG. 23 is a TDD frame defined in the viewpoint of a system A.The frame of FIG. 24 is a TDD frame defined in the viewpoint of a systemB.

Referring to FIG. 23 and FIG. 24, in a TDD frame defined in theviewpoint of the system A, essential control information of the system Acan be defined as a start of a frame, and an RTG (or an idle time) canbe defined as an end of the frame. The essential control information ofthe system A is allocated to a first DL sub-frame, and essential controlinformation of the system B is allocated to a last DL sub-frame.

In a TDD frame defined in the viewpoint of the system B, the essentialcontrol information of the system B can be defined as a start of aframe. Subsequent to a DL sub-frame to which the essential controlinformation of the system B is allocated, a UL frame follows with a TTGbeing located between them. In addition, subsequent to the UL frame, aDL frame starting with a sub-frame to which the essential controlinformation of the system A is allocated follows with an RTG beinglocated between them. An end of the frame can be defined as an end of alast DL sub-frame in a DL frame. Subsequent to the end of the frame, theessential control information of the system follows as a start of a nextframe. When considering a relation of contiguous frames, it is the sameas when the essential control information of the system A is allocatedto a first DL sub-frame in the DL frame and the essential controlinformation of the system B is allocated to a last DL sub-frame in theDL frame. That is, it is the same as when sub-frames in a frame arecyclic shifted so that a DL sub-frame to which the essential controlinformation of the system B is allocated comes first in the frame in theTDD frame defined in the viewpoint of the system A.

Irrespective of whether the TDD frame is defined in the viewpoint of thesystem A or the TDD frame is defined in the viewpoint of the system B,when cyclic shift is performed so that the essential control informationof the system A is allocated to a first DL sub-frame and the essentialcontrol information of the system B is allocated to a last DL sub-framein contiguous DL frames, the number of SSPs can be maintained to one.

FIG. 25 shows another example of control information in a framesupporting heterogeneous systems. FIG. 26 shows another example ofcontrol information in a frame supporting heterogeneous systems. Theframe of FIG. 25 is a DL frame of an FDD frame defined in the viewpointof a system A. The frame of FIG. 26 is a DL frame of an FDD framedefined in the viewpoint of a system B.

Referring to FIG. 25 and FIG. 26, in an FDD frame defined in theviewpoint of the system A, essential control information of the system Acan be defined as a start of a frame, and an idle time can be defined asan end of the frame. The essential control information of the system Ais allocated to a first DL sub-frame, and essential control informationof the system B is allocated to a last DL sub-frame.

In an FDD frame defined in the viewpoint of the system B, the essentialcontrol information of the system B can be defined as a start of aframe. Subsequent to a DL sub-frame to which the essential controlinformation of the system B is allocated, a DL sub-frame for the systemA follows with an idle time being located between them. The essentialcontrol information of the system A is allocated to a first DL sub-frameamong DL sub-frames for the system A. Subsequent to the DL sub-frame forthe system A, a DL sub-frame for the system B follows except for a DLsub-frame to which the essential control information of the system B isallocated. An end of the frame can be defined as an end of a last DLsub-frame among the DL subframes for the system B. It is the same aswhen sub-frames in a frame are cyclic shifted so that a DL sub-frame towhich the essential control information of the system B is allocatedcomes first in the frame in the FDD frame defined in the viewpoint ofthe system A.

Irrespective of whether the FDD frame is defined in the viewpoint of thesystem A or the FDD frame is defined in the viewpoint of the system B,when cyclic shift is performed so that the essential control informationof the system A is allocated to a first DL sub-frame and the essentialcontrol information of the system B is allocated to a last DL sub-framein contiguous DL frames, the number of SSPs can be maintained to one.

A size of the frame for supporting the heterogeneous systems can bedefined such that a plurality of sub-frames are included and at leastone piece of essential control information is included. That is, theframe can be defined as a period of the essential control information.The essential control information of the system A and the system B maybe allocated together in one frame while having either the same periodor different periods. Hereinafter, a case where the essential controlinformation of the system A and the essential control information of thesystem B have different periods will be described.

FIG. 27 shows an example of a super-frame supporting heterogeneoussystems. The super-frame of FIG. 27 is a super-frame in the viewpoint ofa system B when a system A and the system B uses a TDD scheme.

Referring to FIG. 27, essential control information of the system B andessential control information of the system A have a size that is amultiple integer of a period. That is, a size of a frame for the systemB is a multiple integer of a size of a frame for the system A. A periodof the essential control information of the system A can be regarded asa size of frame, and a period of the essential control information ofthe system B can be regarded as a size of super-frame.

The essential control information of the system B is allocated to afirst sub-frame of the super-frame. The essential control information ofthe system B can be regarded as a header of the super-frame. Systeminformation, synchronization information, or the like which is to bebroadcast is allocated to the super-frame header. The super-frameincludes a plurality of frames. The essential control information of thesystem A is allocated to each frame. In the frame in the viewpoint ofthe system A, the essential control information of the system A isallocated to a first sub-frame of the frame, and can be regarded as aheader of the frame. The frame header includes information on resourceconfiguration of the frame. There is no limitation on the number offrames included in the super-frame.

FIG. 28 shows another example of a super-frame supporting heterogeneoussystems. The super-frame of FIG. 28 is a DL super-frame in the viewpointof a system B when a system A and the system B use an FDD scheme.

Referring to FIG. 28, essential control information of the system B andessential control information of the system A have a size that is amultiple integer of a period. A period of the essential controlinformation of the system A can be regarded as a size of frame, and aperiod of the essential control information of the system B can beregarded as a size of super-frame. The essential control information ofthe system B is allocated to a first sub-frame of the super-frame, andcan be regarded as a header of the super-frame. System information,synchronization information, or the like which is to be broadcast isallocated to the super-frame header. The super-frame includes aplurality of frames. The essential control information of the system Ais allocated to each frame. In the frame in the viewpoint of the systemA, the essential control information of the system A is allocated to afirst sub-frame of the frame, and can be regarded as a header of theframe. The frame header includes information on resource configurationof the frame. There is no limitation on the number of frames included inthe super-frame.

In the proposed frame described above, the essential control informationis not limited by definition to minimum control information that must beacquired by a UE using a corresponding system. The essential controlinformation of the system A and the essential control information of thesystem B may consist of the same type of control information or mayconsist of different types of control information. Further, thesuper-frame, the frame, and the sub-frame are not limited in theirsizes. The system A and the system B may use different-sized frames.However, a size of the sub-frame which is a minimum unit of multiplexingthe system A and the system B may be identical between the systems. Inaddition, since the proposed control information allocation method isachieved using DL transmission, a method of multiplexing heterogeneoussystems is not particularly limited in UL transmission. As a radioresource for the essential control information, the entirety or a partof the sub-frame may be allocated. When the radio resource for theessential control information is allocated as a part of the sub-frame, aposition, size, or the like of the essential control information is notlimited in the sub-frame.

According to the present invention, in a frame supporting heterogeneoussystems, essential control information can be fixedly allocated to aspecific position while maintaining the number of system switchingpoints, at which switching occurs between the systems, to one even if aradio resource allocation amount changes between the systems, and thusthe essential control information that must be received by all userequipments can be effectively provided without the increase of overhead.In addition, cell measurement can be performed for handover on the basisof the essential control information allocated to the fixed positionwithout having to detect whether the heterogeneous systems aremultiplexed, and thus overhead caused by control signaling can bedecreased.

All functions described above may be performed by a processor such as amicroprocessor, a controller, a microcontroller, and an applicationspecific integrated circuit (ASIC) according to software or program codefor performing the functions. The program code may be designed,developed, and implemented on the basis of the descriptions of thepresent invention, and this is well known to those skilled in the art.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims. The exemplary embodimentsshould be considered in descriptive sense only and not for purposes oflimitation. Therefore, the scope of the invention is defined not by thedetailed description of the invention but by the appended claims, andall differences within the scope will be construed as being included inthe present invention.

1.-12. (canceled)
 13. A method of transmitting control information in a wireless communication system, the method comprising: allocating a first subset of downlink subframes for a first system in a frame, the first subset including at least one downlink subframe; allocating a second subset of downlink subframes for a second system in the frame, the second subset including a plurality of contiguous downlink subframes; transmitting a frame control header (FCH) in the first subset, the FCH including essential control information for the first system; and transmitting a superframe header (SFH) in the second subset, the SFH carrying essential system parameters and system configuration information for the second system.
 14. The method of claim 13, wherein the second subset is allocated after the first subset.
 15. The method of claim 13, wherein the first subset includes two separate groups of downlink subframes, the each separate group including at least one downlink subframe; and the second subset is allocated between the two separate groups.
 16. The method of claim 13, wherein the number of downlink subframes included in the first subset plus the number of downlink subframes included in the second subset is
 5. 17. The method of claim 13, wherein a ratio of the number of downlink subframes included in the first subset to the number of downlink subframes included in the second subset is one of 3:2, 2:3 or 1:4.
 18. The method of claim 13, wherein the FCH is transmitted in a first downlink subframe in the first subset.
 19. The method of claim 13, wherein the SFH is transmitted in a first downlink subframe in the second subset.
 20. The method of claim 13, wherein a period of the SFH is integer multiple of 40 MS.
 21. The method of claim 13, further comprising allocating a plurality of uplink subframes in the frame.
 22. The method of claim 21, wherein the number of the plurality of uplink subframes is
 3. 23. A method of demodulating control information in a wireless communication system, the method comprising: receiving a superframe header (SFH) which carries essential system parameters and system configuration information in a second subset of downlink subframes, the second subset including a plurality of contiguous downlink subframes in a frame; demodulating the SFH, wherein the frame further include a first subset of downlink subframes, the first subset including at least one downlink subframe; and the first subset and the second subset are for different system respectively.
 24. The method of claim 23, wherein the second subset is allocated after the first subset.
 25. The method of claim 23, wherein the first subset includes two separate groups of downlink subframes, the each separate group including at least one downlink subframe; and the second subset is allocated between the two separate groups.
 26. The method of claim 23, wherein the SFH is transmitted in a first downlink subframe in the second subset.
 27. An apparatus of transmitting control information in a wireless communication system, the apparatus comprising: a radio frequency (RF) unit; and a processor, coupled to the RF unit, and configured to: allocate a first subset of downlink subframes for a first system in a frame, the first subset including at least one downlink subframe, allocate a second subset of downlink subframes for a second system in the frame, the second subset including a plurality of contiguous downlink subframes, transmit a frame control header (FCH) in the first subset, the FCH including essential control information for the first system, and transmit a superframe header (SFH) in the second subset, the SFH carrying essential system parameters and system configuration information for the second system. 